The WMUR poll released Thursday showed 46% of likely voters supported Hassan, 38% for Ayotte, 3% for someone else and 13% undecided. The poll showed Hassan leading among undecided voters as well.

Earlier this week, WMUR released its survey of the presidential race, showing Hillary Clinton leading Donald Trump by 15 points -- a much stronger lead for the Democratic nominee than other polls had found in recent weeks.

The swing-state race is one of several close contests around the county that could decide control of the US Senate, and Ayotte's re-election bid has been complicated further by her party's controversial presidential nominee.

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After initially wavering in support, Ayotte offered her full backing to Trump, who eventually returned it to her. Hassan, who struggled with supporting her own party's nominee, has pounced on the Trump connection.

In particular, she has hammered Ayotte for asserting at a debate that Trump was "absolutely" a good role model for children. The Republican senator later said in a statement that she had misspoken.

Following the revelations earlier this month from a leaked 2005 "Access Hollywood" tape showing Trump bragging about being able to grope women and get away with it, Ayotte pulled her full support of Trump. The Republican presidential nominee's subsequent difficulty in the polls has had some Republicans worried Trump could threaten their hold on Congress.

WMUR's poll, conducted between October 11 and 17, included 770 likely voters reached by telephone, with a margin of error of plus or minus 3.5 percentage points.